1. Field of the Invention
The present invention relates to a lift apparatus, and in particular, a lift apparatus adapted to carry a person up or down along an upright ladder provided in conjunction with a steep surface.
2. Description of the Related Art
It is well known that ladders have been commonly used in order to carry a person or worker up or down along a building wall or other structure.
Recently, attention has been focused on a wind power generation systems as a clean energy source. A windmill for use in wind power generation includes a tower portion and an impeller portion attached to the top of the tower portion. A ladder is provided on the inside of the tower portion as extending vertically from the ground to the wind impeller portion for purpose of maintenance of the windmill.
With large-scaling of a windmill, the ladders can be as high as 60 m and it has been difficult for person to climb or descend such ladders by himself, from the viewpoint of common human physical capabilities.
Under the circumstances, a lift, gondola or elevator apparatus, etc., has been widely used as means for carrying a person up or down along the wall of the tall building.
However, neither of these apparatus can allow the person to climb or descend in the event of failure thereof. On the other hand, in order to install the apparatus on the windmill structure having the existing ladder, removal of the ladder from the windmill structure is often required due to limited space availability.